The Zamenis longissimus (Laurenti) axanthic phenotype found on the Castelporziano Presidential Estate: considerations on its morphology, genetic nature and probable extinction (Serpentes: Colubridae)

Abstract

Two phenotypes—wild and axanthic—of Zamenis longissimus are found on the Roman coast. The axanthic phenotype, in the past erroneously defined as “melanotic”, owes its name to the lack of yellow sub-epidermal pigments, which allows the black effect of underlying melanophores to emerge. These dark specimens seemed to seek out damper habitats compared to those with normal pigmentation, revealing ecological polymorphism. The gradual drying of the climate must therefore have had an impact on their probable extinction (their presence was ascertained in Castelfusano–Castelporziano after 1966 and no later than 1985). In the damp zone, southeast of Torpaterno a pregnant axanthic ♀ was found, with relatively rare genetic features due to a dominant homozygous mutation, deduced from data collected from its offspring and the subsequent cross with ♂ progeny.